Classifications

• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
  • G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
  • G21F9/28—Treating solids
  • G21F9/30—Processing
  • G21F9/301—Processing by fixation in stable solid media
  • G21F9/302—Processing by fixation in stable solid media in an inorganic matrix
  • G21F9/304—Cement or cement-like matrix
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
  • G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
  • G21F9/04—Treating liquids
  • G21F9/06—Processing
  • G21F9/16—Processing by fixation in stable solid media
  • G21F9/162—Processing by fixation in stable solid media in an inorganic matrix, e.g. clays, zeolites
  • G21F9/165—Cement or cement-like matrix

Definitions

• the invention relates to a process for the production of waste solidification products that are ready for disposal and contain radioactive materials with increased radiation resistance or reduced radiolysis gas formation from the category of the radioactive waste molded bodies solidified with hydraulically setting, hardening, inorganic materials, in which radioactive, liquid, aqueous and / or radioactive solid wastes are mixed or coated with a cement-water slurry, allowed to harden and subjected to a heat treatment.
• the waste concentrates is already long been proposed to reduce the volume of such wastes, thereby concentrate the radioactive material to undergo with an addition of glass formers to a heat treatment either to 'spread the radioactive substances in the resulting glass melt. -exist and then allow the melt to solidify to a solid (DE-OS 26 09 299), or to mix with silicate-containing clays or ion exchangers and to burn ceramic to a solid body (DE-PS 27 26 087).
• Cement mixtures are currently used to solidify solid, lumpy waste such as fuel element sleeves or core components.
• the products are not post-treated thermally.
• the disadvantages of cemented high-level radioactive or medium-level radioactive waste, ash, fuel element sleeves and core component products are that, due to the comparatively high water content under the influence of the radioactive radiation emanating from the waste, large amounts of hydrogen and Oxygen are formed. This could be a disadvantage for the Bring operational safety to the interim and final storage.
• the temperatures of the products during storage must be regulated so that they do not exceed 100 ° C. At higher temperatures, water is released from the products, which leads to significant pressure build-up in the product itself and in the container. If the container is corroded, this can lead to the release of activity from the container.
• the invention is based on the object of creating a process for the production of waste solidification products ready for disposal, containing radioactive materials, with increased radiation resistance or reduced radiolysis gas formation from the category of the radioactive waste molded bodies solidified with hydraulically setting, hardening, inorganic materials that all or nearly all the positive properties of the known solidification products also have, but the disadvantages of the known products, in particular the R adiolysegas formation, the pressure buildup in the product or in the container, the risk of activity release from the container or the volatilization of radioactive Do not have nuclides in the production during the high temperature steps etc.
• the object is achieved in a surprisingly simple manner according to the invention in that the mixtures of waste and cement-water slurry in closed containers at a temperature between room temperature can be allowed to harden to shaped bodies up to 150 ° C and that the hardened shaped bodies at a pressure between normal pressure and vacuum are subjected to a heat treatment at temperatures up to a maximum of 250 ° C to remove the unbound water present in the pores of the shaped bodies.
• the waste is mixed or coated with a cement which contains 20 to 30% by weight of SiO 2 and 40 to 70% by weight of CaO, or 25 to 35% by weight of SiO 2 , 10 to 25. wt .-% CaO and 30 to 5 0 wt .-% Al203 contains.
• the cement used can also contain additives such as bentonite.
• a advantageous embodiment of the invention is characterized in that the heat treatment of the shaped body (step c) a temperature between 150 0 and 250 0 C and is carried out over a period of between 12 hours and 4 days.
• the resulting aqueous solutions or aqueous slurries are mixed directly with the cement according to the invention with stirring in a container, which may also be the final storage container, or mixed indirectly in a mixing vessel and then filled into the container.
• the solid, lumpy waste is poured over with a mixture made of cement according to the invention and water (W / Z value advantageously 0.3 to 0.6), possibly using low pressures.
• the hydration (process step b)) is advantageously carried out at temperatures between room temperature and 100 ° C.
• the removal of the excess water (process step c)) is advantageously carried out at temperatures between 100 ° C and 200 ° C.
• the temperature and the duration of the heat treatment are strongly dependent on the composition and dimensions of the products.
• the products should be heated up relatively slowly to avoid cracking.
• the optimal heating and drying times must be adapted to the respective product composition and size. Heating rates in the range between 0.5 C / min have proven to be advantageous. and 2 ° C / min. lie.
• the inventive method Compared to the previous known methods for solidifying the waste solutions or slurries, such as. B. solidification in a glass matrix, etc., the inventive method has a number of significant advantages.
• the process technology for producing the waste products is very simple compared to glazing (mixing in the container by stirring in a separate mixing vessel and filling into the container).
• the hydration of the products and the removal of the excess water takes place at comparatively low temperatures, therefore no radioactive elements escaping via the gas phase, e.g. Cesium and ruthenium.
• Half of the samples from a), b) and c) were produced in accordance with the prior art, ie without heat treatment, only stored for 28 days at room temperature.
• the other half of the samples were heat-treated according to the method of the invention, ie dewatered at 200 ° C.
• all samples were irradiated with 10 MeV electrons up to 10 8 rad and the gas yield measured in ml / g and Mrad.
• the weight loss of the dewatered samples was 23% by weight both in the samples under a) and in the samples under b) and under c). This corresponds to a residual water content of about 7 to 9 G ew .-% in the product.
• Radiolysis gas formation for all samples is shown in the table below.
• M means the weight, weighed after certain time intervals, for the corresponding sample, ⁇ M the weight change in percent of Starting weight. From the table it can easily be seen that after a certain period of time the weight change of the sample with the special cement becomes practically zero, ie after a certain amount of the quinary solution has been taken up, the mass of the sample remains the same. In contrast, the Portland cement sample (which corresponds to the prior art) swells, exhibits a significant increase in mass during increasing storage in the quinary solution and is therefore exposed to increased corrosion.

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• Chemical & Material Sciences (AREA)
• Inorganic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• High Energy & Nuclear Physics (AREA)
• Processing Of Solid Wastes (AREA)

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Publications (3)

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Cited By (8)

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• 1980
  • 1980-12-19 DE DE19803048001 patent/DE3048001A1/de not_active Ceased
• 1981
  • 1981-02-12 EP EP19810100979 patent/EP0054604B1/fr not_active Expired
  • 1981-12-18 BR BR8108271A patent/BR8108271A/pt unknown
  • 1981-12-18 JP JP20601881A patent/JPS57128898A/ja active Pending

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